It's the immigration, stupid: http://anepigone.blogspot.com/2015/11/its-immigration-stupid.html
Polling on immigration often appears to be all over the place. Wording is crucial. When the choices are "deport everyone" and "secure the border and then offer a path to citizenship", the Cathedral can manufacture headlines to try and create an illusion of amnesty as a political winner. When the questions are more objectively designed, it becomes clear that restrictionism is the populist position.

Over the summer, Reuters approached the issue in the most straightforward manner I've ever come across. In terms of fleshing out public sentiment, the approach is bar none. Respondents were asked about what should be done with illegal immigrants in the US. Only two committal answers--"deport most or all of them" and "allow most or all of them to stay"--along with a third "unsure" cop-out option, were offered as responses.